javax.faces.view.facelets.ComponentHandler Maven / Gradle / Ivy
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/*
* Copyright (c) 1997, 2018 Oracle and/or its affiliates. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v. 2.0, which is available at
* http://www.eclipse.org/legal/epl-2.0.
*
* This Source Code may also be made available under the following Secondary
* Licenses when the conditions for such availability set forth in the
* Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
* version 2 with the GNU Classpath Exception, which is available at
* https://www.gnu.org/software/classpath/license.html.
*
* SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
*/
package javax.faces.view.facelets;
import javax.faces.component.UIComponent;
/**
* Public base class for markup
* element instances that map to {@link UIComponent} instances in the
* view.
*
*
*
* Instances of this class are
* created and passed to {@link
* TagHandlerDelegateFactory#createComponentHandlerDelegate} when a tag
* corresponding to this particular component is encountered in a
* Facelet view. A custom tag handler for a component, converter,
* validator, or behavior must extend from this class. In this way,
* this instance acts as a delegate for the implementation private tag
* handler. Such a subclass may choose to override as many or as few
* methods from this base class as desired. If the subclass wants to
* completely override the action of the implementation specific tag for
* which this component is the delegate, it must override the
* apply() method and make it take the following actions,
* in this order. These actions must only happen the first time
* this facelet is applied for each user. Subsequent applications must
* take no action.
*
* The UIComponent represented by this
* element is created with the appropriate
* Application.createComponent() method.
Each attribute specified in the markup is correctly
applied to the component instance, as specified in the VDLDocs
for this element.
If project stage is {@link javax.faces.application.ProjectStage#Development},
Put the {@link javax.faces.view.Location} for this
element into the component attribute Map under
the key given by the value of the symbolic constant {@link
javax.faces.component.UIComponent#VIEW_LOCATION_KEY}.
Set the id of the component. If the id is specified
manually by the page author, that value must be set as the id.
Otherwise, the closest ancestor component that is an instance
of {@link javax.faces.component.UniqueIdVendor} must be
located and its {@link
javax.faces.component.UniqueIdVendor#createUniqueId} method
must be called to derive the id. If no such instance can be
found, call {@link
javax.faces.component.UIViewRoot#createUniqueId} to derive the
id.
The rendererType property of the component is set properly.
{@link #onComponentCreated} is called.
{@link UIComponent#pushComponentToEL} is called on the
newly created component.
The next handler in the facelet chain is applied. This
will cause the component to be populated with children.
The component is added to its parent in the view.
{@link UIComponent#popComponentFromEL} is called on the
newly created component.
Call {@link UIComponent#markInitialState}.
*
* A common use case for extending this class is to gain access to
* the process by which the Facelets runtime creates component instances
* corresponding to markup in a Facelets view. These three methods are
* useful in such cases.
*
* To control the instantiation of the UIComponent
* instance, subclasses may override {@link #createComponent}. If
* this method is not overridden, the tag handler for which this
* instance is the delegate will take the necessary action to
* instantiate the UIComponent.
To be notified of creation of the
* UIComponentinstance, subclasses may override {@link
* #onComponentCreated}.
To be notified that the freshly created
* UIComponent instance has been populated with children as
* a result of execution of child tag handlers, subclasses may override
* {@link #onComponentPopulated}.
*
*
*
* @since 2.0
*/
public class ComponentHandler extends DelegatingMetaTagHandler {
private TagHandlerDelegate helper = null;
private ComponentConfig componentConfig = null;
/**
* Leverage the {@link
* TagHandlerDelegateFactory} provided by the implementation to create
* an instance of {@link TagHandlerDelegate} designed for use with
* ComponentHandler.
*
* @param config the configuration for this handler.
*
* @since 2.0
*/
public ComponentHandler(ComponentConfig config) {
super(config);
this.componentConfig = config;
}
@Override
protected TagHandlerDelegate getTagHandlerDelegate() {
if (null == helper) {
helper = delegateFactory.createComponentHandlerDelegate(this);
}
return helper;
}
public ComponentConfig getComponentConfig() {
return this.componentConfig;
}
/**
* Subclasses that wish to take over
* the task of instantiating the UIComponent instance
* corresponding to this tag handler my override this method to do
* so. A null return from this method will cause the
* TagHandlerDelegate for instance to create the
* component instead.
*
* @param ctx the FaceletContext for this view execution
*
* @return the newly created {@link UIComponent}
*
* @since 2.2
*/
public UIComponent createComponent(FaceletContext ctx) {
return null;
}
/**
* This method is guaranteed to be
* called after the component has been created but before it has
* been populated with children.
*
* @param ctx the FaceletContext for this view execution
* @param c the UIComponent that has just been created.
*
* @param parent the parent UIComponent of the
* component represented by this element instance.
*
* @since 2.0
*/
public void onComponentCreated(FaceletContext ctx, UIComponent c,
UIComponent parent) {
}
/**
* This method is guaranteed to be
* called after the component has been populated with children.
*
* @param ctx the FaceletContext for this view execution
* @param c the UIComponent that has just been
* populated with children.
*
* @param parent the parent UIComponent of the
* component represented by this element instance.
*
* @since 2.0
*/
public void onComponentPopulated(FaceletContext ctx, UIComponent c,
UIComponent parent) {
}
/**
* Determine if the passed component is
* not null and if it's new to the tree. This operation can be used for determining if attributes
* should be wired to the component.
*
* @param component the component you wish to modify
*
* @return true if and only if the argument is not {@code null} and the
* component is new during this run of the lifecycle.
*
* @since 2.0
*/
public static boolean isNew(UIComponent component) {
UIComponent c = component;
if (c != null) {
UIComponent parent = c.getParent();
if (parent != null) {
if (UIComponent.isCompositeComponent(parent)) {
c = parent;
}
}
return c.getParent() == null;
} else {
return false;
}
}
}